Magnetic Properties of theRE2Pt6X15(RE= Y, La–Nd, Sm, Gd–Lu;X= Al, Ga) Series

Abstract

The members of theRE2Pt6Al15(RE= Ce–Nd, Sm, Gd–Yb) andRE2Pt6Ga15(RE= Y, La–Nd, Sm, Gd–Lu) series have been synthesized from the elements via arc‐melting followed by annealing in an induction furnace. Isotypism of Ho2Pt6Al15with orthorhombic (3+1)D commensurately modulated Sc2Pt6Al15[Cmcm(α,0,0)0s0,α= 2/3] was observed from single‐crystal diffraction data. The diffraction pattern shows the same satellite reflections pattern as the prototype, therefore the same modulated superstructure was refined. Full ordering of the Pt and Al atoms within the [Pt6Al15]δ–polyanion was observed. The lattice parameters of the averaged hexagonal structure were refined from powder X‐ray diffraction experiments and agree well with previous reports on these compounds. The X‐ray pure polycrystalline samples of both series were studied with respect to their magnetic properties. The susceptibility data of all investigated compounds show experimental magnetic moments close to the free ion values of theRE3+cations and antiferro‐/ferrimagnetic ordering at low temperatures with Curie temperatures up toTC= 16.8(1) K for Gd2Pt6Ga15. Both, Sm2Pt6Al15and Sm2Pt6Ga15show the typicalvan Vlecktype behavior along with antiferromagnetic ordering at a Néel temperature ofTN= 4.5(1) K (Al) and ferrimagnetic ordering atTC= 6.5(1) K (Ga). Yb2Pt6Al15exhibits ytterbium in the trivalent oxidation state, while for Yb2Pt6Ga15a divalent state of the Yb atoms was observed.